It is known in the food processing industry to use mixing-agitation devices built on the concept of rotating hollow cones, where the liquid is accelerated on the outer and inner sides of the hollow cones. However, since a flow of the liquid product on the inner side of the hollow cones is involved, there is a particle-size limitation that restricts the practical application of these mixing-agitation devices. In fact, these types of mixing-agitation devices are mainly utilized for comminution or micronization.
The subject of rotating cones or conical-surfaces is well known in the literature. For instance, Bruin, S., Velocity Distribution in a Liquid Film Flowing over a Rotating Conical Surface, Chemical Engineering Science 24, pp. 1647-1654, 1969. Under the influence of the centrifugal force, the flow along the surface of a rotating cone causes the liquid to accelerate; essentially, the liquid does flow from the small base towards the large base of the truncated cone. The acceleration of the liquid along the conical surface is a function of the geometry of the conical surface, rotational speed, and flow properties of the liquid. Equally known are the industrial applications of the rotating cones as pumps, degassing devices, level controllers, such as described by Henderson, M. H., Hollow Cone Degassing, US Patent Application 2011/0219853 A1, Sep. 15, 2011.
Commercially available mixing devices operate on the physics of the rotating cones. For instance, in U.S. Pat. Nos. 3,170,638 and U.S. Pat. No. 3,170,639 by Burton, L., a Mixing and Disintegration Head is described. The patents describe a double-cone geometry, where both cones are hollow bodies; that is, the liquid is accelerated on both faces of the hollow cone, the outer face and the inner face. One embodiment discloses a distance piece (i.e. a cage) interposed between the large bases of the two cones, which features elongated openings extending the height of the piece. In another embodiment, there is a flat disc interposed between the large bases of the two cones; the periphery of the disc may be slotted or formed with a plurality of extended teeth; or even the teeth may be serrated in the nature of a rotary saw blade. And then there is another embodiment in which vanes pitched at an angle are installed inside the hollow cones to increases the pumping capacity of the device.
From the point of view of pumping capability, the rotating double-cone devices currently offered on the market have limitations in terms of the particulate size that can pass through the hollow cones; particulates entrained along the outer face of the cones are not limited by the size.
In U.S. Pat. No. 5,407,271 by Jø rgensen, P. J. et al., an Integrated Rotary Mixer and Disperser Head is described. It has a rotating mixing chamber of cylindrical geometry fitted with impeller blades that have ends located outside the mixing chamber to direct the liquid into the mixing chamber and out through some vertical elongated openings made in the wall of the mixing chamber. Similarly, in US Patent Application 2002/0118597 A1 by Korstvedt, H. O., a Mixing Head with axial flow is disclosed. It has a rotating mixing screen of cylindrical geometry that can be fitted with a variety of feeding elements installed at the ends of the screen; these feeding elements may be of different shapes, including flat and conical. The feeding elements include a plurality of openings formed at acute angles relative to the longitudinal axis such that, when rotated, the feeding elements induce liquid flow in an axial direction, inside the rotating screen. The mixing devices described by the Jø rgensen and Korstvedt patents feature entirely internal flow, incompatible with handling of particulates. In fact, these devices are tools mostly intended for comminution or micronization; instead of pumping alone.
Accordingly, there exists a need for a double-cone pumping device that is designed to provide for flow of the liquid product, and making them compatible with mixing of particulate-containing liquid products. Further, there is a need for a double-cone pumping device with large pumping action in mixing-agitation, instead of specific comminution-micronization action. It is therefore an object of the invention to provide a double-cone pumping device aimed at solving these problems, or to at least provide a useful alternative which addresses these needs.